POS0100 TARGETING NF-ΚB SIGNALLING IN B LINEAGE CELLS AS A POTENTIAL NOVEL TREATMENT STRATEGY FOR ANCA-ASSOCIATED VASCULITIS
Authors: A. Merino-Vico, J. P. Van Hamburg, C. Bonasia, P. Heeringa, P. Tuijnenburg, B. Helder, M. Jansen, A. Al-Soudi, H. K. Olsson, N. De Vries, C. Stegeman, J. S. Sanders, A. Rutgers, W. Abdulahad, P. Lyons, T. Bijma, A. Jongejan, T. W. Kuijpers, S. Tas
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> B cells are crucially important in the pathogenesis of many autoimmune diseases, including ANCA-associated vasculitis (AAV), which is further demonstrated by the beneficial clinical effects of rituximab (anti-CD20) B cell targeted therapy. Despite its advantages, this treatment strategy results in long-term B cell depletion and fails to target long-lived plasma cells, rendering an unmet need for more reversible and combined B and plasma cell targeting approaches to achieve long-term disease remission. This aim may be reached by targeting signalling pathways essential for different B cell functions. The canonical and non-canonical NF-κB signalling pathways regulate fundamental B and/or plasma cell responses downstream of various B cell surface receptors, including the B cell receptor, CD40, and TLRs. <h3>Objectives</h3> To study potential alterations in NF-κB signalling in B lineage cells and to evaluate the effects of targeting NF-κB on B cell responses in general, and more specifically on proliferation, plasmablast differentiation and (auto)antibody production in B cells from AAV patients. <h3>Methods</h3> Memory B cells were obtained from AAV patients and healthy donors (HD), and gene expression profiles were generated by RNA-sequencing. Functional assays were performed by culturing PMBCs from AAV patients and HD with stimuli mimicking T cell-dependent (anti-CD40/IL-21) and T cell-independent (CpG/IL-2) conditions. Pharmacological inhibitors of Inhibitor-of-κB-kinase-β (IKKβ, canonical pathway) or NF-κB inducing kinase (NIK, non-canonical pathway) were added to the cultures. Downstream NF-κB signalling was determined by Western blot. After 6-day cultures, B cell proliferation and differentiation were determined by flow cytometry, and ELISA was performed for the detection of (auto)antibody production. <h3>Results</h3> Memory B cells from AAV patients with active disease exhibited an increased expression of NF-κB-associated genes compared to patients in remission and HD. Targeting IKKβ or NIK in AAV and HD B cells effectively blocked downstream canonical or non-canonical NF-κB signalling, respectively. IKKβ and NIK inhibition significantly reduced B cell proliferation in both stimulatory conditions of the functional assay. In addition, IKKβ and NIK inhibitors attenuated B cell differentiation into plasmablasts and antibody production, including anti-proteinase-3 (PR3) autoantibodies. Interestingly, the effects of NIK inhibition appeared to be B cell-specific, as T cell proliferation was largely unaffected. <h3>Conclusion</h3> These data reveal that NF-κB-associated genes are upregulated in memory B cells from AAV patients with active disease and that targeting of NF-κB signalling inhibits B cell responses that are important contributors to the autoimmune process, including autoantibody production. These findings suggest that targeting NF-κB, and particularly NIK, may be developed into a novel more reversible and B cell directed treatment modality for AAV. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Ana Merino-Vico: None declared, Jan Piet Van Hamburg: None declared, Carlo Bonasia: None declared, Peter Heeringa: None declared, Paul Tuijnenburg: None declared, Boy Helder: None declared, Maaike Jansen: None declared, Aram Al-Soudi: None declared, Henric K. Olsson Employee of: Astrazeneca, Niek de Vries: None declared, Coen Stegeman: None declared, Jan-Stephan Sanders: None declared, Abraham Rutgers: None declared, Wayel Abdulahad: None declared, Paul Lyons: None declared, Theo Bijma: None declared, Aldo Jongejan: None declared, Taco W. Kuijpers: None declared, Sander Tas: None declared.